The objective of the proposed 3-year study is to examine the interplay of genetic and environmental influences on conversational language skills and to examine how these etiologic factors relate to other cognitive and academic outcomes. To this end, the proposed research requests funds to transcribe and analyze a total of 1,450 language samples that have been or will be collected as part of the Western Reserve Reading Project (WRRP, Stephen Petrill, P.I., HD38075 &HD46167), a population-based longitudinal study of 350 same-sex twin pairs recruited from the greater Cleveland area as they enter school. In addition to the language sample data, WRRP includes assessments of reading, mathematics, general cognition, socioemotional development, and the family environment. Data will be analyzed using correlational approaches as well as confirmatory model-fitting analyses. The present study is innovative in that it provides the first large-scale twin study of language ability using measures from a conversational context. By analyzing both child and examiner utterances within the conversational exchange, this study will be one of the first to examine the possible influence of evocative gene-environment correlation. In addition, multiple measures within and across developmental domains (e.g., language, reading, math) provide the opportunity to examine the extent of etiologic overlap and specificity-an issue which remains relatively unexplored. Developing a more informed model of how genetic and environmental factors work together to yield language outcomes has important implications for developing programs and strategies that will facilitate child language ability.